Heavy vehicles such as tractor trailers utilize air brakes as the principle means of stopping. These air brake systems generally comprise a service brake utilizing compressed air to actuate the brake mechanism and a spring brake mounted behind the air brake which is actuated mechanically. The spring brake employs a heavy coil spring and functions as an emergency brake anytime there is a loss of air pressure in the service brake. Additionally, the spring brake is a parking brake when the vehicle is stationary.
A problem associated with spring brakes is that the brake assembly being on the underside of a tractor trailer is exposed to harsh weather and road conditions such as snow and salt which results in corrosion of the housing. Such corrosion is severe enough to cause the spring housing to rupture, thereby permitting the spring to be released from the housing. When this occurs, the heavy coiled spring has been known to become a dangerous projectile released from the rear of the vehicle, endangering anything and anyone behind the vehicle. This dangerous situation has been described in a Modern Truck journal article entitled "Coiled Menace A Threat To Highway Safety-" (May 1983) wherein the problem associated with the releasement of spring brakes is discussed. However, the only suggestion for obviating this problem is to periodically check the brake housing for corrosion and to periodically replace the entire housing to avoid the possibility of the housing corroding; but, this is impractical and expensive to do.